[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH V5 2/5] Add XEN pvSCSI protocol description
On 08/20/2014 03:25 PM, Konrad Rzeszutek Wilk wrote: On Mon, Aug 18, 2014 at 11:31:47AM +0200, jgross@xxxxxxxx wrote:From: Juergen Gross <jgross@xxxxxxxx> Add the definition of pvSCSI protocol used between the pvSCSI frontend in a XEN domU and the pvSCSI backend in a XEN driver domain (usually Dom0). This header was originally provided by Fujitsu for XEN based on Linux 2.6.18. Changes are: - added comment - adapt to Linux style guide - add support for larger SG-lists by putting them in an own granted page - remove stale definitions Signed-off-by: Juergen Gross <jgross@xxxxxxxx> --- include/xen/interface/io/vscsiif.h | 214 +++++++++++++++++++++++++++++++++++++ 1 file changed, 214 insertions(+) create mode 100644 include/xen/interface/io/vscsiif.h diff --git a/include/xen/interface/io/vscsiif.h b/include/xen/interface/io/vscsiif.h new file mode 100644 index 0000000..4291889 --- /dev/null +++ b/include/xen/interface/io/vscsiif.h @@ -0,0 +1,214 @@ +/****************************************************************************** + * vscsiif.h + * + * Based on the blkif.h code. + * + * This interface is to be regarded as a stable API between XEN domains + * running potentially different Linux kernel versions. + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to + * deal in the Software without restriction, including without limitation the + * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or + * sell copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER + * DEALINGS IN THE SOFTWARE. + * + * Copyright(c) FUJITSU Limited 2008. + */ + +#ifndef __XEN__PUBLIC_IO_SCSI_H__ +#define __XEN__PUBLIC_IO_SCSI_H__ + +#include "ring.h" +#include "../grant_table.h" + +/* + * Front->back notifications: When enqueuing a new request, sending a + * notification can be made conditional on req_event (i.e., the generic + * hold-off mechanism provided by the ring macros). Backends must set + * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()). + * + * Back->front notifications: When enqueuing a new response, sending a + * notification can be made conditional on rsp_event (i.e., the generic + * hold-off mechanism provided by the ring macros). Frontends must set + * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()). + */ + +/* + * Feature and Parameter Negotiation + * ================================= + * The two halves of a Xen pvSCSI driver utilize nodes within the XenStore to + * communicate capabilities and to negotiate operating parameters. This + * section enumerates these nodes which reside in the respective front and + * backend portions of the XenStore, following the XenBus convention. + * + * All data in the XenStore is stored as strings. Nodes specifying numeric + * values are encoded in decimal. Integer value ranges listed below are + * expressed as fixed sized integer types capable of storing the conversion + * of a properly formated node string, without loss of information. + * + * Any specified default value is in effect if the corresponding XenBus node + * is not present in the XenStore. + * + * XenStore nodes in sections marked "PRIVATE" are solely for use by the + * driver side whose XenBus tree contains them. + * + ***************************************************************************** + * Backend XenBus Nodes + ***************************************************************************** + * + *------------------ Backend Device Identification (PRIVATE) ------------------ + * + * p-devname + * Values: string + * + * A free string used to identify the physical device (e.g. a disk name). + * + * p-dev + * Values: string + * + * A string specifying the backend device: either a 4-tuple "h:c:t:l" + * (host, controller, target, lun, all integers), or a WWN (e.g. + * "naa.60014054ac780582"). + * + * v-dev + * Values: string + * + * A string specifying the frontend device in form of a 4-tuple "h:c:t:l" + * (host, controller, target, lun, all integers). + * + *--------------------------------- Features --------------------------------- + * + * feature-sg-grant + * Values: <uint16_t> + * Default Value: 0 + * + * Specifies the maximum number of scatter/gather elements in grant pages + * supported. If not set, the backend supports up to VSCSIIF_SG_TABLESIZE + * SG elements specified directly in the request. + * + ***************************************************************************** + * Frontend XenBus Nodes + ***************************************************************************** + * + *----------------------- Request Transport Parameters ----------------------- + * + * event-channel + * Values: <uint32_t> + * + * The identifier of the Xen event channel used to signal activity + * in the ring buffer. + * + * ring-ref + * Values: <uint32_t>Should there a bit of explanation here about what 'ring ref' is? Uuh, yes. I'll add it. + * + * protocol + * Values: string (XEN_IO_PROTO_ABI_*) + * Default Value: XEN_IO_PROTO_ABI_NATIVE + * + * The machine ABI rules governing the format of all ring request and + * response structures. + */ + +/* Requests from the frontend to the backend */ + +/* + * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd. + * The target is specified via channel, id and lun. + */ +#define VSCSIIF_ACT_SCSI_CDB 1 + +/* + * Request abort of a running operation for the specified target given by + * channel, id, lun and the operation's rqid in ref_rqid. + */ +#define VSCSIIF_ACT_SCSI_ABORT 2 + +/* + * Request a device reset of the specified target (channel and id). + */ +#define VSCSIIF_ACT_SCSI_RESET 3 + +/* + * Preset scatter/gather elements for a following request. Deprecated. + * Keeping the define only to avoid usage of the value "4" for other actions. + */ +#define VSCSIIF_ACT_SCSI_SG_PRESET 4 + +/* + * Maximum scatter/gather segments per request. + * + * Considering balance between allocating at least 16 "vscsiif_request" + * structures on one page (4096 bytes) and the number of scatter/gather + * elements needed, we decided to use 26 as a magic number. + * + * If "feature-sg-grant" is set, more scatter/gather elements can be specified + * by placing them in one or more (up to VSCSIIF_SG_TABLESIZE) granted pages. + * In this case the vscsiif_request seg elements don't contain references to + * the user data, but to the SG elements referencing the user data.That sounds like the indirect descriptors that virtio and xen-block has. More questions about that below.+ */ +#define VSCSIIF_SG_TABLESIZE 26 + +/* + * based on Linux kernel 2.6.18, still valid + * Changing these values requires support of multiple protocols via the rings + * as "old clients" will blindly use these values and the resulting structure + * sizes. + */ +#define VSCSIIF_MAX_COMMAND_SIZE 16 +#define VSCSIIF_SENSE_BUFFERSIZE 96 + +struct scsiif_request_segment { + grant_ref_t gref; + uint16_t offset; + uint16_t length; +};Yeey, 8 byte data structure!+ +/* Size of one request is 252 bytes */ +struct vscsiif_request { + uint16_t rqid; /* private guest value, echoed in resp */ + uint8_t act; /* command between backend and frontend */ + uint8_t cmd_len; /* valid CDB bytes */ + + uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE]; /* the CDB */ + uint16_t timeout_per_command; + uint16_t channel, id, lun; /* (virtual) device specification */ + uint16_t ref_rqid; /* command abort reference */ + uint8_t sc_data_direction; /* for DMA_TO_DEVICE(1) + DMA_FROM_DEVICE(2) + DMA_NONE(3) requests */ + uint8_t nr_segments; /* Number of pieces of scatter-gather */ +#define VSCSIIF_SG_GRANT 0x80 /* flag: SG elements via grant page */ + /* nr_segments counts grant pages with + SG elementsStop missing. However I am a bit lost. It says that the 'nr_segments' will have the count of grant pages with SG elements. Does that mean the req.seg[0].gref points to an page which will have an array of grant references? And each grant reference will point to a data page? What about the 'offset' and 'length' of them? Or does it mean that the 'reg.seg[0].gref' points an page that is filled with 'struct scsiif_request_segment' ? If so, where would the could of those segments be in? In 'nr_segments'? If that is so where does the VSCSIIF_SG_GRANT go? Won't we collide? nr_segments (without the VSCSIIF_SG_GRANT bit) always counts the number of populated seg[] entries. If VSCSIIF_SG_GRANT is set, each seg[] entry references another array of struct scsiif_request_segment using a grant ref, offset into the granted page and a length of the array in bytes. The resulting number of struct scsiif_request_segment is the sum of seg[0..nr_segments-1].length / sizeof(struct scsiif_request_segment). + usable if "feature-sg-grant" set */ + + struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE]; + uint32_t reserved[3];Or is the flag suppose to show up here? No. There is no guarantee an "old" domU not aware of "feature-sg-grant" will have set reserved[] to zero. +}; +The previous structure had an comment about the size of the structure. Should it be here as well? I can add one. +struct vscsiif_response { + uint16_t rqid; /* identifies request */ + uint8_t padding; + uint8_t sense_len; + uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE]; + int32_t rslt; + uint32_t residual_len; /* request bufflen - + return the value from physical device */ + uint32_t reserved[36]; +}; + +DEFINE_RING_TYPES(vscsiif, struct vscsiif_request, struct vscsiif_response); + +#endif /*__XEN__PUBLIC_IO_SCSI_H__*/ _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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